@inproceedings{ML-1989-AllenL,
	author        = "John A. Allen and Pat Langley",
	booktitle     = "{Proceedings of the Sixth International Workshop on Machine Learning}",
	isbn          = "1-55860-036-1",
	pages         = "229--231",
	publisher     = "{Morgan Kaufmann}",
	title         = "{Using Concept Hierarchies to Organize Plan Knowledge}",
	year          = 1989,
}